Projectors are devices that project images onto surfaces where they can be viewed. Often these projectors are used to project images onto walls of a room to assist with a presentation. This presentation may, for example, occur when a presenter is presenting to an audience.
Conventional projectors project an image in one direction; this image is usually located on a wall that is behind the presenter (where it is visible to the audience, but not to the presenter). This location of the image requires the presenter to turn his/her back to the audience to view the visual.